无法将哈希图转换为字符串

Question

这很奇怪，因为我遇到了一个错误，指出无法将哈希图转换为字符串，但是我没有在该文件中使用任何哈希图，并且我认为哈希图可以很好地用于在数据库中存储值，但是有时产生空异常错误。我对此并不陌生，并且已经阅读了一些相关主题，但是找不到任何解决方案，并且我的logcat中没有显示很多错误...

我认为某些值是null，但不知道如何解决.....我认为我应该使用getter和setter方法，但它们倾向于产生null错误

 ublic class ListViewActivity extends AppCompatActivity {

    private ListView listview;
    private EditText edit;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_list_view);

        listview = findViewById(R.id.listView);
        edit = findViewById(R.id.edit);




        final ArrayList<String> list = new ArrayList<>();
        final ArrayAdapter adapter = new ArrayAdapter<String>(this, R.layout.list_item, list);



        listview.setAdapter(adapter);



        DatabaseReference reference = FirebaseDatabase.getInstance().getReference(); // getReference() is the root
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                list.clear();
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                    String names = String.valueOf(snapshot.child("Name").getValue());
                    String addresses = String.valueOf(snapshot.child("Address").getValue());
                    String suburbs = String.valueOf(snapshot.child("suburbs").getValue());
                    String states = String.valueOf(snapshot.child("State").getValue());
                    String phones = String.valueOf(snapshot.child("Phone_No").getValue());
                    String postcodes = String.valueOf(snapshot.child("Postcode").getValue());
                    String doctors = String.valueOf(snapshot.child("Doctor").getValue());

                   Information info = snapshot.getValue(Information.class);
                    assert info != null;
                    String txt = info.getName() + " , " + info.getAddress() + " ," + info.getSuburb() + " , " + info.getState() + " , " + info.getPhone_No() + " , " + info.getPostcode() + " , " + info.getDoctor();
                    list.add(txt);


                    //      list.add(snapshot.getValue().toString());
                }

                adapter.notifyDataSetChanged();

            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {

            }
        });
    }



}